In today's medical world, physicians are moving more and more toward treatment that is evidence-based. For the patient, this means there is reasonable "proof" that the proposed treatment is going to work. Some treatment is easier to study and evaluate than others.

For example, in this study, surgeons compared the results of using a low dose (20 mg) steroid injection versus high-dose (40 mg) injection for patients with shoulder pain. They included a third (control) group who received a placebo injection. All 90 patients who were divided into these three groups had shoulder pain. They also had loss of motion associated with a diagnosis of subacromial impingement or subacromial impingement syndrome (SIS).

Subacromial impingement refers to pinching of the soft tissues (bursa, tendons) that pass underneath the acromion (the roof of the shoulder). Although SIS is one term, it actually represents a wide range of underlying pathologies. There could be a bursitis, rotator cuff tendinopathy, fracture, calcific tendinitis, or other change in the local anatomy contributing to the problem.

There are many factors that add up together to cause subacromial impingement syndrome. Aging with its many degenerative processes isn't always very kind to the shoulder. Bone spurs form, the rotator cuff and other soft tissues fray and wear thin, and trauma all add to the development of mechanical shoulder pain. Loss of blood supply to the area is another reason why these problems occur.

No matter what brings on the impingement syndrome, the end result is always the same: shoulder pain with movement. There is also loss of the normal gliding action required for movement of the arm overhead. Treatment often includes steroid injections so it's important to know whether this approach works and the best way to administer it.

That's where this study comes in. Other studies have shown the value of corticosteroid injections as a means of reducing inflammation and reducing pain. With accurate injection into the bursa, success has been reported in up to 83 per cent of patients. Now it's up to research science to determine the exact dosages that work best.

The two dosages selected for study (20 mg and 40 mg) are the most commonly used injections. A long-acting medication (triamcinolone acetonide) was used for both. Higher doses have a greater risk of complications but may work faster. Lower doses may not deliver enough medication to make a difference. Everyone in this study received one injection based on the group they were randomly placed in (high-dose, low-dose, placebo).

The injection was delivered using real-time ultrasound so the surgeon could be accurate in placing the needle right into the bursa. Results were measured on the basis of pain, motion, and perceived disability. Two questionnaires were used to measure outcomes (e.g., Visual Analog Scale, Shoulder Disability Questionnaire).

Everyone was followed at two-week intervals for eight weeks. At first, they were cautioned against any heavy lifting or exercise. But after two weeks, they were encouraged to start gentle range-of-motion exercises and to remain active. Additional strengthening exercises were added four weeks after the injections.

They found that the low-dose had just as good of results as the higher dose injections. Effects lasted the full eight weeks in the low-dose group. Complications and negative effects were minimal in both groups. One person experienced dizziness. Another reported facial flushing three days after the injection. But there were no skin or joint infections or changes in skin color where the needle went through.

The authors concluded that low-dose corticosteroid injection for subacromial impingement is just as effective as high-dose and with fewer side effects. Physicians no longer have to rely on their own experience to determine optimal dosages for their patients.

It is suggested that the low-dose injection be used as the first injection on a trial basis. Since many patients get up to three injections spaced apart, a low-dose injection could be followed by a higher-dose injection if results of the first injection are not satisfactory.

To conclude, the authors suggested a few directions for future research in this area. First, it would be helpful to know which shoulder pain patients would benefit the most from steroid injections. For example, do acute patients with early symptoms get the same (more, less?) results compared with patients who have chronic shoulder pain (lasting more than six months). In other words, if there isn't active ongoing inflammation, should steroid injections even be used at all?

Next, different doses of steroid need to be evaluated. Just because 20mg gave the same results as 40mg doesn't mean 20mg is the best (optimal dose) for everyone. Maybe it's possible to go even lower. Maybe some shoulder problems would respond better at a low-dose while others need a higher-dose injection.

And finally, although studies show the benefit of exercise for subacromial impingement, there are no studies proving what type is best. And that raises all kinds of additional questions. What is the best timing for exercise following cortisone injections? Does exercise work better with low-dose versus high-dose cortisone shots?

For now we know there is evidence to suggest the benefit of low-dose over high-dose cortisone injection for subacromial impingement. A treatment plan can be developed around this information. Further refinements can be made as more research is done to answer some of these other questions.